Robots are commonly used for a range of industrial tasks, and also for performing surgery. Robots can operate purely under programmatic control or they can be configured to respond to inputs in real time from a user interface. In the most complex and critical tasks, such as surgery, it is normal for a robot to operate under real-time command of an operator. To achieve this, the operator is presented with a suitable input mechanism. This is typically a physical mechanism that can be moved by the operator in three dimensions. The control system of the robot senses the configuration of the input mechanism. The control system is programmed to cause the robot arm/manipulator to move in response to the sensed configuration of the control mechanism. Additionally, it is normal for the robot to present to the user a visual indication of the state of the robot, to help the operator understand what inputs are required to achieve a certain task. The visual indication may be a video stream captured by a camera on or near the robot arm and presented to the operator on a display screen.
Some tasks that might be performed by a robot in this way require significant dexterity on the part of the user. An example of such a task is performing suturing using a surgical robot. It may be necessary to make fine and precise sutures using instruments attached to surgical robot arms, whilst the instruments are constrained within a working cavity in the body of a patient. Forming such sutures by means of a user interface of the type described above can place extreme demands on the operator's precision of movement. This can be time-consuming, extending the time for which the patient is under surgery and making the operator more tired.
One proposal for addressing this problem has been to automate tasks of this nature. For example, “Autonomous Suturing using Minimally Invasive Surgical Robots” (H Kang and J Wen, Proc. 2000 IEEE Int. Conf. on Control Applications) discusses algorithms for performing automatic robotic suturing. Approaches of this type suffer from a number of problems. First, whilst it may be feasible to automatically suture on well-characterised substrates, for example substantially planar tissue joins, it is considerably harder to automate suturing on more complex structures. In addition, a skilled surgeon may modify the size and placement of sutures depending on his knowledge of neighbouring features such as blood vessels. Second, many delicate surgical tasks are not standardised and must be adapted to an individual operation. For example, in hand surgery it may be necessary to perform a procedure on a certain part of a tendon when access to that point is hampered by bones, nerves etc. Since those obstacles vary depending on the patient, such a task is infeasible to automate.
Most people are more able to perform complex tasks with one hand than with the other. The majority of people are right-handed. When a right-handed operator is controlling a surgical robot he will typically be better able to control the robot to perform delicate tasks using his right hand. However, the nature of the surgical operation may be such that the robot arm or instrument that has to be moved in a delicate way is being controlled by the operator's left hand. In this situation some robotic user interfaces will allow the operator to lock the right-hand arm or instrument so that the user can transfer his right hand to the controller for the left-hand arm or instrument. However, in this configuration the user is no longer able to move both arms or instruments simultaneously.
There is a need for an improved way of controlling a robot.